How to set a shape's background in xml?

I just created a red circle using android shapes:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:innerRadiusRatio="4"
    android:shape="ring"
    android:thicknessRatio="9"
    android:useLevel="false" >

     <solid android:color="#FF0000" />

    <size
        android:height="48dip"
        android:width="48dip" />

</shape>

This is really cool, but I cannot set the background color of the circle to my color. I tried android:background="#FFFFFF" but it always appear to be black in my layout. How can I set the background of the above shape?

I think a layer-list might help you:

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >

    <item>
        <shape android:shape="rectangle" >
            <solid android:color="#ffffff" />
        </shape>
    </item>
    <item>
        <shape
            android:innerRadiusRatio="4"
            android:shape="ring"
            android:thicknessRatio="9"
            android:useLevel="false" >
            <solid android:color="#FF0000" />
            <size
                android:height="48dip"
                android:width="48dip" />
        </shape>
    </item>

</layer-list>

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">

    <corners android:radius="12dp" />
    <solid android:color="#ffffff" />
    <stroke
        android:width="1dp"
        android:color="@android:color/black" />

</shape>

I am just adding helpful research as an answer. Let us suppose you have a shape as the answer described by @GeneBo and you are looking forward to re-using that shape but with a different solid color. So all you need to do in your widget is:

android:background="@drawable/your_shape_to_reuse"
android:backgroundTint="@color/new_background_color_you_need"